Sonic dredging process and apparatus



March 7, 1967 A. G. BODINE, JR 3,307,278

SONIC DREDGING PROCESS AND APPARATUS Filed Nov. 24, 1964 4 Sheets-Sheet1 March '7, 1967 A. G. BOBINE, .IR 3,307,278

SONIC DREDGING PROCESS AND APPARATUS i A Filed Nov. 24, 1964 4sheets-Sheena I Il I1: lf. l1 P so I 2 k: 8l

IN VENTOR.

March 7, 1967 A. G. BOBINE, JR

SONIC DREDGING PROCESS AND APPARATUS 4 Sheets-Sheet 5 Filed Nov. 2,4,`1964 March 7, l967 A. G. BOBINE, JR 3,307,278

SONIC DREDGING PROCESS AND APPARATUS Filed Nov. 24, 1964 4 Sheets-Sheet4 INVENTOR.

United States Patent Office Patented Mar. 7, 1967 3,307,278 SONICDREDGING PROCESS AND APPARATUS Albert G. Bodine, Jr., 7877 Woodley Ave.,Los Angeles, Calif. 91406 Filed Nov. 24, 1964, Ser. No. 413,495 21Claims. (Cl. 37-195) This application is a continuation-in-part of myprior copending application Serial No. 299,209, filed August 1, 1963,now Patent No. 3,189,536, and of my parent application Serial No.739,291, filed June 2, 1958, now Patent No. 3,123,546, of which saidapplication Serial No. 299,209 was a continuation-in-part.

This invention relates generally to methods and apparatus for dredgingthe bottoms of bodies of Water, such as lakes, harbors, rivers, etc., byapplication of one or more sonic principles. These sonic principlesinvolve elastic vibrations in elastically vibratory systems, thetransmission of elastic waves or Vibrations therein or therealong, sonicphenomena occurring between two sonic wave transmission media,vibrations in the basi-c apparatus at resonant frequency and the effectsof these sonic phenomena on earthern materials Worked on in dredging,both before and after separation thereof from the bottom or banksholding the body of water. The general object of the invention is toprovide improved methods and apparatus for dredging, relying uponeffects gained through use of such sonic principles.

In accordance with the invention, a sonic elastically vibratory actionis applied to a shoe, cutter or bit member which is positioned adjacentor engageable with the earth at the bottom of the Water. In a preferredform of the invention, the bit member is carried at the lower end of adredge tube which participates in the sonic, elastic vibrations.standing wave vibration is set up in the dredge tube, This vibration inand along the dredge tube keeps the dredge solid material in suspensionin the water present, and acts also to reduce the friction at the wallsof the tube so as to facilitate flow of the mixture of dredged solidmaterial and water up the tube.

In addition,the sonic vibratory action transmitted down the dredge tubeis applied to vibrate the shoe or bit at the bottom. Here the shoe orbit applies the sonic energy to the earth material to accomplish any oneor all of several results, such as cutting and/or fracturing earthmaterial loose from the bottom, and stirring up such separated earthmaterial, and/or already loosened earth material, overburden, or ore,such that such materials become suspended in the water, and thusavailable or accessible for transmission up the dredge tube. Theinvention includes as an important step or feature the establishment ofa cir-culatory'ow stream of water up the dredge tube, so as to carry upthe loosened particles of earth material or ore.

The sonic vibratory action is very effective in stirring and mixing theearth material and water. Sonic waves are transmitted into the water aswell as into the earth material with a resulting violent mixing actionthat generates a mud slurry capable of being circulated up the dredgetube.

The earth material fatigues and disintegrates rapidly under sonicvibration, helped along by the presence of water, which is cyclicallyinjected and caused to penetrate into the soil, between thesoilparti-cles, so that they rapidly break apart.

Preferably, for example, resonant longitudinal As stated above, the bitor shoe transmits sonic vibratory energy into the water. The resultingsonic vibratory commotion in the water has a violent stirring,cavitating and agitating effect, stirring and sweeping up earthparticles, overburden, ore, or newly broken loose or fragmentedmaterial, into suspension so as to be picked up by the flow stream goingup the dredge tube. This commotion in the water results largely fromacoustic coupling of the vibratory bit to the water. In thisperformance, sound waves are radiated from the bit into the water, notonly downwardly but laterally. The sonic action can also be transmittedto the Water from the side walls of the lower region of the dredge tube,especially if there is a substantial component of lateral wave sonictransmission in the tube. The acoustic impedance (defined ratio ofvibratory pressure amplitude to velocity amplitude in the media) of thewater and the velocity of sound therein are sufficiently close to thoseof the coupling surfaces on the bit or tube to assure good transmissionof acoustic energy into the water. In turn, the sound waves so radiatedinto the water reach and are transmitted into the earth. A usefulphenomenon here is that there are suficient differences between theacoustic impedances and velocities of sound for water and earth mediathat sonic wave reflections and relative movements and stresses in themedia occur, creating a condition highly conducive to disintegration andstirring up of the earth material. The activity can be heightened bydriving the system hard enough to cause the vibrations to take place ata suficient amplitude to bring about the violent conditions ofcavitation, and such constitutes one preferred practice of theinvention.

The conditions described in the preceding paragraph can be brought aboutwith the bit or shoe positioned close to but spaced from the earthenbottom or formation, or with the bit or shoe pressed thereagainst. Withthe shoe or bit pressed tightly against the virgin earth material orformation, a large flow of sonic vibratory energy goes directly into theearth material or formation, and under these conditions earth material,even hard rock, can be caused to disintegrate rapidly by fatiguefailure.

The invention will be further described with reference to theaccompanying drawings showing illustrative embodiments thereof, andwherein:

FIG. l is a side elevational View, partly in medial section, showinglargely diagrammatically an illustrative embodiment of the invention;

FIG. 2 is a plan view taken in accordance with the arrows 2--2 of FIG.1;

FIG. 3 is a section on line 3--3 of FIG. 2;

FIG. 4 is a view similar to FIG. 1 but showing a modification;

FIG. 5 is -an end elevational view of the apparatus shown in FIG. 4,looking toward the right in said figure;

FIG. 6 is a transverse section taken on line 6 6 of FIG. 4; and

FIG. 7 is a section taken on line 7-7 of FIG. 6.

Referring first to FIG. 1, the numeral 10 designates generally a dredgebarge floating in a body of water 11, and thus forming -a floatingplatform for the equipment. This body of water stands against an earthbank 12 rising thereabove in the right-hand portion of the picturethereabove, and opposite to bank 12 is an underwater bank 13.

-The banks 12 and 13 defining a channel which has been dredged out andwhich has a bottom 15. The barge 10 may be equipped with conventionalpropulsion and maneuvering equipment, not shown.

Erected on barge 1t) is a frame structure 16 rising from a bed frame 17,and the latter has at one end of the barge an overhanging or outwardlyprojecting bracket 18, formed with an aperture 19 which receives avertically disposed dredge tube Ztl. The dredge tube 20 is composed ofan elastic, elastically vibratory substance, preferably steel. It hasfixed to its top end a mounting plate or flange 21 for vibratinggenerating means designated generally at 22.

The vibration generating means 22 is driven from a drive shaft 24powered by an internal combustion engine 2S mounted on the framestructure 16.

The upper end portion of dredge tube 20 has an outlet to which iscoupled a discharge hose 26 leading to the inlet of a centrifugal pump27 driven by a small internal combustion engine 23. The pump outletconnects to a discharge pipe 29, which is shown as coupled to a hose 30,discharging on land beyond the bank 12. Alternatively, the hose 341could of course discharge to another barge, or to a suitable pipeline,or otherwise, as desired. The pump 27 and engine 2S are mounted on aportion 32 of framework 16, as illustrated.

The upper end portion of dredge tube 20 is connected by parallel links33 to a vertical component 34 of frame structure 16, and these linkskeep the dredge tube 20 in a generally vertical position.

Vertically positioned tube 20 has fixed thereto the piston 36 of an airspring device 37, the latter comprising, in addition to the piston 36, acylindrical :piston housing 38 which is mounted on the aforementionedbracket 18. The housing 38 has a lower wall 38a which is apertured toslidingly pass the dredge tube 20, packing being used at 40, asillustrated. Packing 41 seals the piston 36 to the housing 3S. Air underpressure is introduced into the chamber housing 38 by an air line 37afrom any suitable source of pressurized air, not shown, and the airpressure maintained inside the chamber of the air spring will beunderstood to be such as will counterbalance all or a predeterminedproportion of the weight of the dredge tube 20 and other parts mountedthereon. This air spring 37 cushions the dredge tube, and isolates itsvibration from the barge.

The dredge tube 20 extends downwardly through the body of water nearlyto the bottom where the dredging operation is to be carried out.Surrounding the dredge tube 2t?, with annular clearance, as shown, is ajacket pipe 44, and screwed to the lower end thereof is a shoe, cutteror bit member 46 which is engageable with the earth material at thebottom, and also, in this embodiment of the invention, is engageablelaterally with the bank 13 for cutting away of the latter. Acousticallyspeaking, this member 46 constitutes a sonic wave coupler and radiator.The details of this particular illustrative member 46 will be describedhereinafter. i

The lower end of dredge tube 2t) has an external annular flange 47,which is received between internal annular flanges 48 and 49 securedinside the l-ower end portion of the jacket pipe 44. Near the upper endof jacket pipe 44 said pipe has an internal annular ange 50 which isspaced slightly from pipe 2t) and which functions as a centering meansor guide. At the upper end, the jacket pipe 44 has an inwardly turnedange 51 which is close spaced to the tu-be 2t).

Mounted inside dredge tube 2t) is a long venturi tube 52, the lower endportion of which is disposed closely adjacent the bit member 46, and iswelded inside the flange 49. The upper end of venturi tube 52 is well upthe dredge tube 26, and is welded thereto as at 52a.

The drive shaft 24 extends from engine 25 into suitable bearings 55within a gear case `60, and carries inside case 60 a spur gear 61. Onthe other side of gear case 60, the shaft extends through universaljoints 62 and 63 to a vibration generator unit 22a forming one componentof the generating means 22. Spur gear 61 meshes with a second spur gear64 in gear case 60, and the latter is on a shaft 66 which extendsthrough universal joints 67 and 68 to the second vibration generatorunit 2lb of the generating means 22. The two generator units 22a and2211 may be identical and a detailed description of one will suffice forboth. The generator 22a has 4a housing 70 made up of an intermediateblock 71 and two end caps 72 and 73, together with a spacer 74 lbetween4block 71 and cap 73, said members being of rectangular shape as seen inthe aspect of FiG. 3.

The members 71 to 74 are secured in assembly with one another by bolts72a. A bore 75 extends through block 71 `and is continued a shortdistance into end cap 72. and spacer 74. Mounted on this bore 75 is ahard steei raceway cylinder 76, in which is a cylindrical raceway bore77. Washers 78 are preferably used in end cap 72 and spacer 74 at theends of the cylinder 76. Cylinder 76 and washers 78 thus define acylindrical raceway for a hardened steel cylindrical inertia roller 80,which is of somewhat lesser diameter than the internal diameter' oflbore 77, and is adapted to roll around the inside of the bearingsurface defining said bore 77.

Inertia roller 80 has an axial bore 81 which rotatably receives an axle82 projecting axially from a spur gear S4. The pitch circle of gear 84corresponds to the diante' eter of inertia roller 80, and this gear 84meshes with a stationary internal gear 86 which is formed in theaforementioned spacer member 74. The internal gear 86 has a pitch circlecorresponding with raceway bore 77.

Projecting from spur gear 84 is a cup SSin which is `formed an internalgear 89, and this internal gear 89 meshes with a spur gear 96 on the endof drive sha-ft 24 the latter being journaled in the hub 92 of end Gap73`J coaxially with raceway 77 The inertia roller S0 will be understoodto fit closely but with working clearance within the overlappingportions of the washers 78. In operation, inertia roller 80 rolls aroundraceway bearing surface 77, and is held in engagement therewith bycentrifugal force. While the generator is at rest, or coming up tospeed, the roller S0 is maintained in close adjacency to bearing surface77 by means of inter-engaging conical axial projections g4' and 95 onthe gears 84 and 90, respectively.

Operation is as follows: Rotation of shaft 24 turns the spur gear 90,which, being in engagement with inl' ternal gear 8% on one side, causesrotation of the latter, The gear 84 integra-l with the thus-driven gear89 is1 int mesh with internal gear 86, and when driven, rolls around theinside of gear 86. Inertia roller 80 is thereby caused to roll aroundthe inside of cylindrical bearing surface 77. As mentioned, when thegenera-tor is up to speed, Cen trifugal force developed by the rotationof the krol-ler gti causes it to bear with considerable pressure againstthe bearing surface 77, and a substantially non-slipping, roll-v ingengagement is thereby attained. As will appear, roller Sti rolls `aroundthe inside of cylindrical bearing surface 77 substantia-lly in step withthe rolling of the spur gear 84 around the internal gear S6. Anytendency for roller St) to describe this orbital path with a differentrate of rotation on its axis from the ,rotation of spur gear 84 on theaxis of the latter is accommodated by a slight rotation of roller 30 onthe axle 32.

The centrifugal force developed by the relatively heavy inertia roller86 rolling in its orbital path around the inside of bearing or raceway76 results in exertion of a substantial gyratory force on Vthe vibratorhousing 70. This gyratory force is transmitted from the generatorhousing 76 to the platform 21 on the upper end of dredge tube 2t). InView of the fact that there are two of the generator units 22a and 22hmounted on the platform 21, two gyratory force outputs are transmittedfrom the two generators to the platform 21, and the net effect on theplatform 21 depends upon the phase relationship of the inertia roll ersSti of the two generator units. Since the drive shafts 4 and 66 for thetwo generator units are geared together to turn in opposite directions,the inertia rollers 80 roll around their respective raceways in oppositedirections, as indicated by the `arrows in FIG. 3. In addition, in theillustrative embodiment, the rollers 80 may be so phased as to movevertically in unison or in step with one another, but laterally inopposition to one another. Accordingly, lateral components ofcentrifugal force generated by the two inertia rollers 80 are cancelledout, whereas longitudinal or vertical components are additive. In netresult, a vertically oriented alternating output force, such asindicated by the double headed arrow f in FIG. 3, is applied by the twogenerator units 22a and 22h to the platform 21 and therefore to theupper end of the dredge tube 20.

The sonic wave or vibration generating means 22 composed of the units22a and 22b is driven by engine 25 at a speed to generate itsalternating output force at a frequency at which a longitudinal,resonant, elastic standing wave is set `up in the dredge tube 20, to theupper end of which this alternating output force is applied, in avertical direction, as just explained. The generating means 22 willgenerate a half-wavelength longitudinal standing wave in the tube 20 ifits frequency is made substantially equal to S/ 2L, where S is the speedof sound in the material of the tube and L is its equivalent length.Such halfwavelength standing wave operation is the fundamental mode ofoperation, and is preferred, though harmonic frequencies may be employedif desired. Assuming, however, the half-wave mode of standing wavevibration, the tube 20, under the influence of the alternating forceimpulses exerted on its upper end, alternately elastically elongates andcontracts. The center region stands nearly sta tionary, the wave at thispoint having a node or pseudonode. The upper and lower end portions ofthe dredge tube, on the other hand, vibrate through magnifieddisplacement distances, and these regions of the wave are known asvelocity antinodes. A half-wavelength longitudinal standing wave patternof the kind here referred to is depicted at W in FIG. 4 showing amodified apparatus. The housings of the vibration generator units 22aand 22b will be seen to vibrate vertically at the amplitude encounteredat the upper velocity antinode. Obviously, this vibration cannot betransmitted back through the shafts 24 and 66 to the gear housing 60because of the universal joints in said shafts, though said shafts doswing vertically with the generator housings, accommodated by thuniversal joints therein.

It'is in some cases desirable to cause the dredge tube to vibrate wit-ha lateral component of vibration. This can be accomplished with thepresent apparatus by omitting one of the generator units 22a or 22b, ormaking the inertia roller 80 of one of the units more massive than thatin the other. Alternatively, the phasing of the two inertia rollers 86can be adjusted for a lateral Wave output, in a known manner. Thevibrations transmitted in the dredge tube will then have components bothlongitudinally and laterally of the dredge tube. Moreover, the frequencycan be chosen for resonant standing wave vibration in either thelongitudinal mode, as before, or in the lateral mode. The lateral modeis effective for transmitting sonic action into the water.

In effect, the shoe or bit 46 is on the lower extremity of theelastically vibrating dredge tube 20, at the point of the lower velocityantinode therein, and vibrates with this low-er extremity of the dredgetube. Usually, the principal mode of vibration is longitudinal, and thisvibration of the shoe or bit 46 is then vertical. This vibration maytake place with the .shoe or bit 46 on bottom, as illustrated, orseparated a short distance above bottom, though ordinarily, the bit 46is held firmly against the bottom. In addition to thus vibratingvertically against bottom, or closely adjacent thereto, the bit 46 ispreferably given a slow oscillation about a vertical axis through apredetermined arc of travel. This may be accomplished by a rod 96pivotally connected at one end to a pin 97 set into and projectinglaterally from one side of jacket 44, and having at its opposite end aneccentric strap 98 surrounding an eccentric 99 driven from a smallinternal combustion engine E.

The bit, in the present illustrative embodiment, comprises a lower endformed by downwardly directed bit teeth 46. The throw of the eccentric99 is preferably made such that the teeth 46 will work back and forthover the surface of the earth material or rock structure below them. Thestroke should be at least equal to the distance between adjacent teeth.

In addition, in the preferred embodiment here illustrated, the bit 46 isformed with an exterior bellows-shape comprised of alternating circularridges 46c and depressions 46d. These ridges and depressions have twoseparate functions, first, to work against the bank and cut materialtherefromV while undergoing the previously described vertical vibration,and, second, as acoustic coupling means to the surrounding water. Thevertically projected area of the bellows formations will be understoodto act as sonic wave radiators, radiating acoustic energy into thesurrounding water. Because of the angular disposition of theseformations, this acoustic agitation also is directed somewhat angularlyoutwardly from the bit 46. The projected downwardly facing surfacesincluding the areas between the bit teeth at the bottom of the bit alsoact as acoustic coupling means to the water and as sonic energyradiation means, and sonic radiation occurs from these surfaces whetheror not the bit is in engagement with the bottom 1S.

In dredging service, the shoe or bit 46 on the lower end of the dredgetube 20 is positioned usually firmly against the bottom structure 15,taking advantage of at least a part of the weight of the jacket 44, thedredge tube 20 itself, and the generator means 22 mounted at the top.All or part of this weight can of course be counterbalanced by airpressure inside air spring 37. Thus, sufficient air pressure can bebuilt up inside the chamber of the air spring to counterbalance theentire weight of the dredge tube and parts mounted thereon, so that, forexample, the dredge tube can be supported with its bit olf bottom. T-heair spring, in this aspect, may be regarded as representative of a meansfor vertical positioning of the dredge tube. It will thus be clear thatthe air spring does afford a means for raising or lowering the dredgetube, and it will be evident to those skilled in the art how, bysuitable, easily contrived reorganization, greater range of verticalmovement can be achieved. It will also be clear that a larger range ofvertical movement may be readily provided by incorporating suitableelevator means in the dredge tube supporting structure. For example,t-he whole supporting frame structure, or any necessary subcomponentthereof, can readily be provided with means for vertical adjustment.Such arrangements, being readily understood and well within the skill ofthe art, will not be necessary to be further illustrated or describedherein. It will further be understood that, in practice, dredge tubes ofdifferent lengths may be provided and used interchangeably iin theapparatus, according to the necessary dredging depths in any givenpractical situation.

With this understanding, it will be clear that, using such facilities ormethods as referred to, the dredge tube is rst positioned into thedesired proximity to the bottom 15, and normally, or ordinarily, thisinvolves actual forcible mechanical engagement with the bottom. Further,the quantity of air delivered into the air spring and the pressureestablished therein is usually, or preferably, such as to counterbalancea desirable share of the weight of the dredge tube and parts mountedthereon, so as to attain the desired position or force of the bit onbottom. With such conditions established, the vibratory dredge tube 20is partially supported by the cushion of air contained in the airspring, and the vibration of the dredge tube thus is well isolated fromthe frame platform.

The apparatus being thus positioned, and the ygenerator means 22 beingin operation, the longitudinal standing wave is set up in the dredgetube 20, causing the bit 46 to vibrate vertically on bottom 15. Severaladvantageous performances are attained. First, the shoe or bit vibratingagainst bottom structure or formation 15 sets the latter into sonicvibration at an amplitude of the same approximate order as the bit. Thissonic vibration causes the earth material to fatigue and disintegraterapidly. Moreover, this fatigue and disintegration process is promotedby the presence of the water, which, because of acoustic coupling to thevibratory bit, is subject to cyclic oscillation and thus cyclicallyinjected and caused to penetrate into the soil, between the soilparticles, so -as to force them to break apart. This fracturing effect,by fatigue action, is particularly promoted when the bit is forced verytightly against the formation, so that when fatigue action anddisintegration are particularly desired, the process will generallyconsist in or include the step of maintaining the shoe or bit forciblyagainst the bottom formation. Further, the sonic energy applied to theformation has the effect of stirring up such separated earth material,-and/or already loosened earth material, overburden, or ore, such thatsuch materials become suspended in the water, and thus available oraccessible for transmission up the dredge tube. This stirring up andsuspension action is further very importantly promoted by sonic wavecommotion or vibration in the water around the shoe or bit and thebottom formation or loose material thereon. Such sound wave commotion orvibration results, of course, from acoustic coupling of the shoe or bitto the water and such coupling takes place from the downwardly andlaterally facing formations on the bit, such as th-e annular downwardlyand -outwardly facing bellows surfaces 46e, and such as the downwardlyfacing edge surfaces between the bottom engaging bit teeth 46a and 46h.Of course, such sound wave radiation into the water takes placeirrespective of whether the -bit is in engagement with the bottom.Accordingly, one process in accordance with the invention is to operatewith the bit slightly off bottom, relying upon the sound wave radiationinto the water and loose earth material on bottom to stir up suchmaterial yand carry it into suspension in the water so that it can bereadily picked up and circulated up the dredge tube.

The above described lateral sonic vibration of the dredge tube, whenused, is especially beneficial if the dredge is progressed along thebottom of the body of water. Here the sonic action may be radiatedeffectively against the ledge or bank 13 so as to cut and mix sonicallyin a forward direction as the barge progresses along.

To accomplish good transmission of `acoustic vibratory energy from thevibr-ation generating means 22 at the top of the dredge tube to theformation at the bottom, and to the water surrounding the shoe or bit,requires that consideration be given to the matter of acoustic impedancein the equipment. Acoustic impedance is defined as the ratio of themagnitude of cyclic force amplitude to cyclic displacement velocity, andit is first of all important that the generator means be designed tohave an acoustic impedance which is comparable with that of thevibratory dredge tube 2t) at the point of coupling therebetween. It willof course be readily apparent that a steel tubing, such as the dredgetube 20, will have a large acoustic impedance, since a large axial forcemust be applied to such a tube to elastically compress it and move itsupper end axially through a short displacement distance. A vibrationgenerating means of comparable acoustic impedance is mandatory if goodenergy transmission is to be accomplished from the generator into thedredge tube. Acoustic generator units of the type herein provided areadmirably suited to this application, since they comprise a relativelylarge mass which moves a short displacement distance but with high forcewhen coupled to the system to be vibrated thereby. In brief,

.earth material.

8 the requirement that the vibration generating lme-ans and the dredgetube have output and input impedances, respectively, which are of thesarne order, is well satisfied by the particular generating means hereindisclosed for present illustrative purposes.

Second, it is also of importance that the output imped ance of thevibratory system, at the point of coupling with the earthen formation,have a magnitude of the `same order as that of the earthen structure tobe vibrated. The output impedance of the bit on the lower end of thedredge tube Zt is of an order of magnitude sufficiently matched toearthen rock structure to assure effective transmission of acousticenergy from the bit into the formation.

The output impedance at the bit, however, is of somewhat greatermagnitude than the impedance of the water to which the bit isacoustically coupled, though the differences in impedance are not sogreat las to prevent good radiation of acoustic energy into the water.Large wave radiation into the water immediately surrounding and underthe bit is thus accomplished, and this vibratory sonic energy in thewater is very effective in promoting the agitation, stirring andsweeping up of the loose accumulation of earth material on the rockbottom 15, so that such material goes into suspension. Final-ly, thesound waves radiated from the shoe or bit into the water reach and aretransmitted into the earth. There are sufficient differences between theacoustic impedances and velocities of sound for water and earth mediathat sonic wave refiections and relative movements and stresses in themedia occur, particularly at the interface between the water and theearth. These conditions create a condition highly conducive todisintegration and stirring up of the The sonic vibrations areheightened by driving the system hard enough to cause the vibrations totake place at an amplitude great enough to cause sonic cavitation,causing an even greater order of agitation, stirring up, and breaking upof the earth material, all to the end of bringing such material intosuspension in the water.

By the practices of the invention, a violent stirring and mixing actionis produced that generates a mud slurry capable of being circulated upthe dredge tube. When this slurry has been produced, it is circulated upthe dredge tube by operation of centrifugal pump 27, as previouslydescribed. An increasein flow velocity obtained by use of the venturitube 52 aids in keeping the ymaterial in suspension. Thus, broadly, theinvention comprises the use of acoustic waves for stirring up of earthenmaterial into the water, and then the pumping of the resulting slurry upthe dredge tube.

With further reference to the venturi tube 52, which is an optional butpreferred feature, when this tube is used, it elastically elongates andcontracts with the portion of the dredge tube 20 within which it iswelded, both top and bottom. it accordingly becomes a Iunitary part ofthe dredge tube and moves correspondingly therewith in vibratory action.The vibratory action of the interior surface is also useful in reducingfriction between the upwardly circulated stream or column of earthmaterial in suspension in water with the lining surface of the dredgetube. This frictional drag against the upwardly owing stream of slurryis normally quite material, and is reduced to a relatively negligiblefactor by the vibratory action produced in the practice of theinvention.

The dredging operation has been described in the foregoing primarily inthe aspect of breaking up the earthen formation at the bottom, stirringup such material into suspension in the water, and then circulating itup the dredge tube. Also mentioned has been the process of operatingwith the shoe or bit somewhat off bottom 15, where the effect isprimarily to stir loose material already on bottom, bring it into goodsuspension, and then circ-ulate it up the dredge tube. The process mayalso be used, as intimated earlier, to cut back the bank 13 by verticalvibration of the laterally projecting ridge formation 45C of the bitwhen 'these formations are laterally engaged with the bank.

Reference is next directed to FIGS. 4-8, showing an alternative4embodiment of the invention, which is particularly intended fordredging up ore, such as gold, along river bottoms, though of course itwill be understood that the invention is not restricted to that specificapplication. The apparatus in this case uses a relatively small float 90in place of the fairly sizable barge of the earlier embodiment, and thisoat 90 is shown floating in body of water 91 standing over river bottom92. The bottom at 92 is to be understood as typically the hard uppersurface of bed rock or other strata, which may be covered over to somedepth by a more easily penetrable overburden 93 which is at the bottomof the body of water 91. It may be stated that an accomplishment of theinvention is to gain access to ore lying on the bottom hard layer 92through the overburden 93, without the necessity of first removing suchoverburden.

The dredge tube is designated generally in this instance by thereference num-eral 96, and is positioned on an incline, with its upperend portion over one edge portion of the float, and its lower endprovided with a shoe 98 working on or positioned in operative relationto bottom 92. In this embodiment, the shoe 9S is provided with asupporting roller 98a which rolls on bottom 92 and properly positionsthe shoe relative to the bottom. The dredge tube 96 is provided with ajacket pipe 99 which extends from a point somewhat short of the upperend of the dredge tube to a point along the dredge tube well down intothe water, typically as indicated in FIG. 4. Upper and lower spacerrings 100 and 101 connect the upper and lower ends of jacket 99 to thedredge tube 96.

The dredge tube 96, a later described sonic vibration generator mountedthereon, and the jacket 99 are all supported, in the present instance,by means of a U-shaped or horseshoe-shaped vibration isolation spring104 which is connected to the bottom of spacer ring 100 on one side, andto the underside of a sloping rife board 105 on the other. Riffle board105, provided with riies 105a of a conventional nature, is in turnsupported from the oat by means of bent leaf springs 106 and 107.Isolation spring 104 largely isolates the vibration in dredge tube 96from the riile board, but does transmit a useful amount of 1ongitudinalvibration to the rife board` for effective separation of the heavier orefrom sand and rock. This heavier material is collected in the pockets ofthe ritile board, as at 1051). The two springs 106 and 107 fairlyeffectively isolate the vibration in the riffle board from the oat, sothat the latter is Inot strongly shaken. The dredge tube jacket is shownto be provided with handles 108.

The vibration generator, designated generally by reference numeral 109,and whose interior details will be described presently, is here shown toembody a generally rectangular housing 110 mounted on a mounting plate111, which in turn seats on a platform or filler plate 112 locatedbetween the underside of plate 111 and the upper side of the upper endportion of dredge tube 96, which ripper end portion will be seen to havea curve therein so as to discharge horizontally onto the upper end ofriiiie board 105. Cap screws 113 extend downwardly through mountingplate 111, filler block 112, and into the dredge tube 96 to secure thegenerator 109 firmly to the upper end portion of the dredge tube.

Generator 109 is an air-driven type, having air intake hose 115 leadingfrom an air compressor 116 driven from lan internal combustion engine117, the compressor 116 and engine 117 `being mounted on a commonplatform 118, supported by arches 119 mounted on float 90. Spent airfrom generator 109 is conducted via discharge pipe 120 to the upper endof the annular jacket space 121 inside jacket 99, flowing downwardlywithin this space to ports 122 formed in dredge lnube 96 inside thejacket but near the lower end shoe 98. This air mixes with the waterinside dredge pipe 96, lightening its density, so that an up- 10 wardcirculation of the water and material in suspension therein isestablished within the dredge tube. It will be clear that with thedensity of the fluid in the dredge tube reduced by the presence of theair thus circulated therethrough, the hydrostatic pressure on theexterior body of water will force a flow upwardly through the pipe 96.

The vibration generator 109 is shown more particularly in FIGS. 6 and 7.The housing 110 has a cylindrical raceway therein, and within andcoaxial with this raceway is a pipe 131, closed at one end, and coupledat the other to air supply pipe 115. Pipe 131 has tangential dischargejets 133 extending from its interior bore to its exterior periphery.Surrounding the pipe 131 is a gyratory ring 134, of a diameter somewhatlarger than the outside diameter of the pipe 131 and such that, when inengagement on one side of the pipe 131, it just slightly clears thesurface of the bore 130 on the opposite side. Air under pressureentering the bore of pipe 131 is ejected in tangential direction towardthe ring 134, and drives the ring s0 as to spin or whirl on the pipe131, in the direction of the arrow, as indicated in FIG. 6. The spentair, after impinging on the ring 134, escapes from within the ring byway of grooves 136 formed in the side walls of the housing, and thendischarges by way of outlet passage 137 leading to the aforementionedhose 120.

The shoe 98 shown for illustrative purposes is of a type which might becompared to a vacuum cleaner nozzle, having an open aperture `98b at thebottom spaced shortly above the supporting rock l'ioor 92 by wheel 98a.In other applications, the shoe can be modified, and can, for example,be given cutter or cutting bit characteristics, and be arranged forengagement with and acoustic coupling to the structure of the floor orbottom 92, or merely, in some cases, to the overburden 93 on floor 92.

It will be noted that this nozzle 98 has a lower edge which will engagewith projections of the earthen structure 92, to apply sonic energythereto and cause sonic cutting in the manner of a sonically activatedbit. Various teeth members of the type shown in connection with FIG. 1may be formed in this lower edge, as shown. Deletion of roller 98a, ifdesired, will increase this bit cutting action.

The operation of the modified system of FIGS. 4 8 is in general respectsimilar to that of FIGS. l-3. The vibration generator 109 clamped to theupper end of elastic dredge tube 96 applies to said dredge tube agyratory force, one component of which is oriented longitudinally of thedredge tube, and the other laterally of the dredge tube. The generatoris driven at the frequency for resonant, longitudinal, half-wavestanding wave vibration of the dredge tube, producing a half-wavelengthstanding wave in the dredge tube as diagramrned at W in FIG. 4. Thecomponent of the gyratory output force of the vibration generator whichis a right angles to the longitudinal axis of the dredge tube createslateral or transverse vibration in the dredge tube, but since, ingeneral, the resonant standing wave frequencies for longitudinal andlateral vibrations differ considerably from one another, if thegenerator is driven at the Ifrequency for longitudinal resonantvibration, such frequency will ordinarily be somewhat removed from theresonant frequency for lateral resonant vibration. Accordingly, thedredge tube may Abe vibrated predominantly in the longitudinal standingwave mode, though some lateral vibration will be attained. Thelongitudinal standing wave, as diagrammed in FIG. 4, is preferred, butuseful effects can also be obtained by tuning for a lateral standingwave, which constitutes an alternative practice of the invention.

In FIG. 4, the shoe on the lower end of the dredge tube is not of acutter type, and is, in fact, supported above rock bottom 92 by roller98a. Sonic wave radiation takes place from the shoe, which is inacoustic coupling Irelationship to the water, and sound wave action isthus transmitted into the water, producing the stirring and agitatingeffect described in connection with the earlier embodiment of theinvention. The dredge tube is shown, for illustrative purposes, in thiscase, as reaching down through a layer of loose or soft overburden 93,as earlier described, so as to work on hard bottom 92. The describedstirring and agitating action as a result of sound wave radiation fromthe shoe brings this overburden material, as well as sand and rock onbottom, together with particles of ore resting on bottom, up intosuspension in the liquid immediately below or within the shoe. Acirculation of liquid is established up the dredge tube by which thissuspended material, inclusive of the ore particles raised off bottom,may be lifted up the dredge tube. This may of course be accomplished byuse of the system illustrated in FIG. l, namely, by use of a centrifugalpump. The system of FlG. 4, however, shows an alternative arrangement bywhich the air exhausted from the Vibration generator is used to reducedensity and establish this circulation of water and suspended materialup the dredge tube, as describe-d in more particular hereinabove. Thus,the suspended material is circulated up the dredge tube, and depositedon the riflie boar-d 195, along which it travels to the discharge endthereof. This ritile board receives a degree of vibration from thestanding wave vibration in the dredge tube 99, sufficient to promotedropping of the high-density ore particles into the pockets between theriffies.

yThe over-all action is unique, in that the lower end of the dredge tubeis moved along the river bottom through the overburden, parting thelatter and working directly on bottom, so as to pick up the valuable oremost likely to be found in that location.

It will of course be understood that various modifications of the shoe98 may be employed, and the shoe may drag directly on the bottom, mayhave cutter teeth thereon, or even be pressed against 1bottom oracoustically coupled thereto in any desired manner.

It will be understood that the drawings and descriptions are merelyillustrative of the invention in presently conceived |forms, and thatvarious changes in design, structure, and arrangement may be madewithout departing from the spirit and scope of the broad invention or ofthe claims appended hereto.

I claim:

1. In a sonic apparatus for dredging earth material from the earthenbottom of a body of water, the combination of:

a dredge tube extending downwardly to a position adjacent to saidearthen bottom,

a resonant sonic vibration radiator at the lower end of said dredge tubelfor stirring up earthen material at said bottom and bringing it intosuspension in the water so as to form a slurry adjacent said lower endof said dredge tube,

a resonant elastic vibration system vibratorily coupled to saidradiator,

sonic generating means for driving said sonic wave radiator, saidgenerating means Ibeing operable at a frequency which will produce Sonicwave vibration, and

means for circulating said slurry up said dredge tube.

2. The apparatus of claim 1, including means causing forcible engagementof said sonic radiator means with said earthen bottom below said body ofwater.

3. The apparatus of claim 1, including means supporting said sonicradiator means with a gap between said radiator means and the earthenbottom below said body of water.

4. The apparatus of `claim 2, wherein said sonic radiator meanscomprises a bit.

5. In a sonic apparatus for dredging earth material from the earthenbottom of a body of water, the combination of:

a platform for floating on said body of water,

an elastically vibratory dredge tube extending downwardly from saidplatform to a position adjacent to said earthen bottom,

a vibratory sonic wave radiator shoe coupled to the lower end of saiddredge tube so as to vibrate therewith,

sonic vibration generating means acoustically coupled to the upper endof said dredge tube for setting up sonic resonant standing wavevibration in said dredge tube and thereby vibrating said sonic waveradiator shoe, said generating means being operable at a frequency whichwill produce sonic wave vibration, and

means for circulating slurry up said dredge tube.

6. The subject matter of claim 5 wherein said vibration generator meansis operable at a frequency for a longitudinal mode of standing wavevibration in said dredge tube.

7. The subject matter of claim 5 wherein said vibration generator meansis operable at a frequency for a lateral mode of standing wave vibrationin said dredge tube.

8. The subject matter of claim 5, including dredge tube support meansaffording forcible engagement of said sonic radiator shoe with saidearthen bottom below said body of water.

9. The subject matter of claim 5, wherein said radiator means comprisesa bit.

10. The subject matter of claim 5, including spring means yieldinglyvertically supporting said dredge tube from said platform.

11. The subject matter of claim 10, wherein said spring means comprisesan air spring.

12. The subject matter of claim 5, wherein said means for circulatingslurry up the dredge tube comprises a slurry discharge conduit connectedto the upper end portion of said dredge tube and a pump connected intosaid discharge conduit.

13. The subject matter of claim 5, wherein said means for circulatingslurry up the dredge tube comprises a means for introducing a gas into alower rregion of said dredge tube.

14. The subject matter of claim 5, including also a venturi tube linerin said dredge tube.

15. The subject matter of claim 5, wherein said radiator means comprisesa bit rotatably mounted relatively to the lower end of said dredge tube,and including also means for rotating said bit.

16. The subject matter of claim 5, wherein said radiator means comprisesa bit rotatably mounted relatively to the lower end of said dredge tube,and including also means for oscillating said bit about the longitudinalaxis of said dredge tube.

17. The subject matter of claim 5, including also an elongated jacketrotatably surrounding a substantial length of said dredge tube belowsaid platform, said wave radiation shoe being fixed to said jacket androtatable therewith relatively to said `dredge tube, and means forpreventing relative longitudinal movement of said lower end of saiddredge tube and said shoe.

1S. The subject matter of claim 5, including means on said shoe forsupporting it on and at a predetermined distance above bottom.

19. The apparatus of claim 1 wherein said generating means is operableat the resonant frequency of said resonant elastic vibration systemcoupled to said generating means and said radiator.

2d. The process of sonic dredging which includes:

coupling a sonic frequency resonator to a sonic vibration radiatormeans;

positioning said radiating means adjacent the bottom of a body of water;

operating said resonator at sonic frequency so as to activate saidradiator means for sonically stirring up earthen material at saidbottom; and

conducting water with said stirred-up earthen material up a dredge owpassage from the region of said stirred-up earthen material.

21. The subject matter of claim 20, including also the step of pressingsaid radiator means forcibly against said Ibottom.

FOREIGN PATENTS 697,311 11/1964 Canada'. 72,377 11/ 1943 Czechoslovakia.References Cited by the Examiner 1,069,453 2/1954 France.

UNITED STATES PATENTS 5 10/ 1887 Howell 35-58 ABRAHAM G. STONE, PrimaryExaminer.

4/ 1909 Eiiel et a1. 37-58 12/1936` Ram-my 37 195 X JOE O- BOLT, Exmme5/1951 Bodine. t E 11/1961 Skakel et al. ,57195 10 J. R. OAKS, Asszs antxamznef.

1. IN A SONIC APPARATUS FOR DREDGING EARTH MATERIAL FROM THE EARTHENBOTTOM OF A BODY OF WATER, THE COMBINATION OF: A DREDGE TUBE EXTENDINGDOWNWARDLY TO A POSITION ADJACENT TO SAID EARTHEN BOTTOM, A RESONANTSONIC VIBRATION RADIATOR AT THE LOWER END OF SAID DREDGE TUBE FORSTIRRING UP EARTHEN MATERIAL AT SAID BOTTOM AND BRINGING IT INTOSUSPENSION IN THE WATER SO AS TO FORM A SLURRY ADJACENT SAID LOWER ENDOF SAID DREDGE TUBE, A RESONANT ELASTIC VIBRATION SYSTEM VIBRATORILYCOUPLED TO SAID RADIATOR, SONIC GENERATING MEANS FOR DRIVING SAID SONICWAVE RADIATOR, SAID GENERATING MEANS BEING OPERABLE AT A FREQUENCY WHICHWILL PRODUCE SONIC WAVE VIBRATION, AND MEANS FOR CIRCULATING SAID SLURRYUP SAID DREDGE TUBE.